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mockdata

Go

A command-line mock data generator written in Go. Define your data schema in a YAML config file and generate realistic test data as JSON, CSV, or SQL INSERT statements.

Table of Contents

Installation

git clone https://github.com/kumarvv/mockdata.git
cd mockdata
go build -o mockdata .

Usage

./mockdata <config-file>

Example:

./mockdata sample.yml

The tool reads the YAML config file, generates data according to the schema, and writes output files to the directory specified in to_path. Output files are named <table_name>.<target_type> (e.g., users.json, tags.csv, orders.sql).

Configuration File

Config files are written in YAML with two top-level keys: target and tables.

target:
  type: json              # Output format: json | csv | sql (required)
  to_path: /output/dir   # Directory to write output files (required)

tables:
  - name: users           # Table/file name (required)
    row_count: 100        # Number of rows to generate (optional, default: 1)
    columns:
      - column_name: function_name(param1=value1,param2=value2)
      - id: uuid()
      - name: random_full_name()

Target Fields

Field Required Description
type Yes Output format — json, csv, or sql
to_path Yes Directory path where output files are written

Table Fields

Field Required Description
name Yes Table name; used as the output file name
row_count No Number of rows to generate (default: 1)
columns Yes List of column definitions as column_name: function_expr pairs

Column Syntax

Each column is a key-value pair where the key is the column name and the value is a function expression:

- column_name: function_name(param1=value1,param2=value2)

Parameters are comma-separated key=value pairs inside parentheses. For functions that take a single value parameter, the shorthand positional form works too:

- status: string(active)         # shorthand
- status: string(value=active)   # explicit

Target Types

json

Generates a JSON array of objects written to <table_name>.json.

target:
  type: json
  to_path: /output

Output example (users.json):

[
  {
    "id": "a1b2c3d4-...",
    "name": "Jane Smith",
    "email": "jane.smith@example.com"
  }
]

csv

Generates a CSV file with a header row written to <table_name>.csv. Values are quoted and escaped automatically.

target:
  type: csv
  to_path: /output

Output example (users.csv):

id,name,email
a1b2c3d4-...,Jane Smith,jane.smith@example.com

sql

Generates SQL INSERT statements written to <table_name>.sql. Table names are lowercased. String values are quoted.

target:
  type: sql
  to_path: /output

Output example (users.sql):

INSERT INTO users (id, name, email) VALUES ('a1b2c3d4-...', 'Jane Smith', 'jane.smith@example.com');

Function Types

Static / Literal

These functions output a fixed value on every row.

Function Parameters Description Example
string value (required) Static string string(active)
integer value (required) Static integer integer(42)
float value (required) Static float float(3.14)
boolean value (required) Static boolean — true, false, y, yes boolean(true)
date value (required) Static date in YYYY-MM-DD format date(2024-01-15)
datetime value (required) Static datetime in YYYY-MM-DD HH:MM:SS format datetime(2024-01-15 09:30:00)
sql value (required) SQL expression (requires DB connection) sql(NOW())

Usage:

columns:
  - source: string(IMPORT)
  - version: integer(1)
  - price: float(9.99)
  - is_active: boolean(true)
  - start_date: date(2024-01-01)
  - created_at: datetime(2024-01-01 00:00:00)

Sequence

Function Parameters Description Example
uuid none Generates a UUID v4 uuid()
serial start (optional, default: 1) Auto-incrementing integer starting from start serial(start=100)

Usage:

columns:
  - id: uuid()
  - seq_num: serial()
  - order_num: serial(start=1000)

Names & Identity

Function Parameters Description Example
random_title gender, case Random title (Mr., Mrs., Dr., etc.) random_title(gender=female)
random_first_name gender, case Random first name random_first_name(gender=male)
random_last_name case Random last name random_last_name()
random_full_name gender, case Random full name random_full_name()
random_gender case Random gender (male or female) random_gender()

Parameters:

  • gender — male or female; if omitted, randomly selected per row
  • case — upper or lower; if omitted, mixed case is used

Usage:

columns:
  - title: random_title(gender=female)
  - first_name: random_first_name()
  - last_name: random_last_name(case=upper)
  - full_name: random_full_name(gender=male)
  - gender: random_gender()

Contact & Location

Function Parameters Description Example
random_email case, domain Random email address random_email(domain=example.com)
random_phone none Random phone number random_phone()
random_address case, country Random full street address random_address()
random_street case Random street name random_street()
random_city case, country Random city name random_city(country=US)
random_state case, country Random state (full name) random_state(country=US)
random_state2 case, country Random state abbreviation (2-char) random_state2()
random_country case Random full country name random_country()
random_country2 case Random 2-char country code random_country2()
random_country3 case Random 3-char country code random_country3()
random_currency case Random currency code random_currency()

Parameters:

  • case — upper or lower
  • country — country filter (e.g., US)
  • domain — custom email domain (e.g., mycompany.com)

Usage:

columns:
  - email: random_email()
  - work_email: random_email(domain=acme.com)
  - phone: random_phone()
  - address: random_address()
  - street: random_street()
  - city: random_city(country=US)
  - state: random_state()
  - state_code: random_state2()
  - country: random_country()
  - country_code: random_country2()
  - currency: random_currency(case=upper)

Numbers

Function Parameters Description Example
random_number min, max Random integer in range random_number(min=1,max=100)
random_decimal min, max Random decimal (float) in range random_decimal(min=0,max=9.99)
random_range min, max Random number within range random_range(min=10,max=50)
random_boolean none Random true or false random_boolean()

Usage:

columns:
  - age: random_number(min=18,max=99)
  - score: random_decimal(min=0,max=10)
  - quantity: random_range(min=1,max=500)
  - is_verified: random_boolean()

Dates & Times

Function Parameters Description Example
random_date format Random date; default format 2006-01-02 random_date(format=2006-01-02)
random_day none Random day of month (1–31) random_day()
random_month none Random month name random_month()
random_year none Random year (1900–2999) random_year()

Note: The format parameter for random_date uses Go's reference time: 2006-01-02 15:04:05.

Usage:

columns:
  - birth_date: random_date()
  - event_date: random_date(format=01/02/2006)
  - day: random_day()
  - month: random_month()
  - year: random_year()

Random Choice

Pick a random value from a pipe-separated list of options.

Function Parameters Description Example
random_in_string value (required) Random string from |-separated list random_in_string(admin|user|viewer)
random_in_integer value (required) Random integer from |-separated list random_in_integer(1|2|3|4|5)
random_in_float value (required) Random float from |-separated list random_in_float(0.5|1.0|1.5|2.0)

Usage:

columns:
  - role: random_in_string(admin|editor|viewer)
  - status: random_in_string(active|inactive|pending)
  - priority: random_in_integer(1|2|3)
  - discount: random_in_float(0.05|0.10|0.15|0.20)

Text

Function Parameters Description Example
random_string len, min, max, case Random alphanumeric string random_string(len=10)
random_paragraph len, min, max, case Random paragraph of text random_paragraph(min=50,max=200)

Parameters:

  • len — exact character length
  • min / max — random length between min and max characters
  • case — upper or lower

Usage:

columns:
  - token: random_string(len=32,case=upper)
  - username: random_string(min=5,max=15)
  - bio: random_paragraph(min=100,max=500)
  - notes: random_paragraph(len=200,case=lower)

Advanced

Function Parameters Description Example
random_format numOfPairs, separator Formatted random string pairs joined by separator random_format(numOfPairs=3,separator=-)
random_from_sql value (required) Random value from a SQL query result (requires DB connection) random_from_sql(SELECT id FROM products)

Usage:

columns:
  - tracking_code: random_format(numOfPairs=4,separator=-)
  - product_id: random_from_sql(SELECT id FROM products ORDER BY RANDOM() LIMIT 1)

Sample Files

JSON Output — User Records

Generates 10 user records as a JSON file.

target:
  type: json
  to_path: /tmp/mockdata

tables:
  - name: users
    row_count: 10
    columns:
      - id: uuid()
      - seq: serial()
      - title: random_title(gender=male)
      - first_name: random_first_name()
      - last_name: random_last_name()
      - full_name: random_full_name()
      - gender: random_gender()
      - email: random_email()
      - phone: random_phone()
      - address: random_address()
      - city: random_city()
      - state: random_state2()
      - country: random_country2()
      - username: random_string(len=12,case=lower)
      - role: random_in_string(admin|editor|viewer)
      - rating: random_in_integer(1|2|3|4|5)
      - score: random_decimal(min=0,max=100)
      - is_active: boolean(true)
      - source: string(WEB)
      - created_at: random_date()

Sample output (users.json):

[
  {
    "id": "f47ac10b-58cc-4372-a567-0e02b2c3d479",
    "seq": 1,
    "title": "Mr.",
    "first_name": "James",
    "last_name": "Peterson",
    "full_name": "James Peterson",
    "gender": "male",
    "email": "james.peterson@randommail.com",
    "phone": "555-867-5309",
    "address": "742 Evergreen Terrace",
    "city": "Springfield",
    "state": "IL",
    "country": "US",
    "username": "jamesp2024ab",
    "role": "editor",
    "rating": 4,
    "score": 73.42,
    "is_active": true,
    "source": "WEB",
    "created_at": "2023-07-14"
  }
]

CSV Output — Tag Records

Generates 5 tag records as a CSV file.

target:
  type: csv
  to_path: /tmp/mockdata

tables:
  - name: tags
    row_count: 5
    columns:
      - uuid: uuid()
      - username: random_string(len=25,case=upper)
      - full_name: random_full_name(gender=male)
      - email: random_email()
      - created_at: random_date()
      - sys_key: string(ABCD)
      - is_active: boolean(true)
      - version: integer(123)
      - rating: random_in_integer(1|2|3|4|5)

Sample output (tags.csv):

uuid,username,full_name,email,created_at,sys_key,is_active,version,rating
f47ac10b-58cc-4372-a567-0e02b2c3d479,XKQZRMJWDNLFPVHBCEAYTOU,James Peterson,james.peterson@randommail.com,2023-07-14,ABCD,true,123,3

SQL Output — Order Records

Generates 20 order records as SQL INSERT statements.

target:
  type: sql
  to_path: /tmp/mockdata

tables:
  - name: orders
    row_count: 20
    columns:
      - order_id: uuid()
      - customer_id: uuid()
      - status: random_in_string(pending|processing|shipped|delivered|cancelled)
      - total_amount: random_decimal(min=10,max=9999)
      - item_count: random_number(min=1,max=20)
      - currency: random_currency(case=upper)
      - ship_country: random_country2()
      - notes: random_paragraph(min=10,max=80)
      - created_at: random_date()
      - is_paid: random_boolean()

Sample output (orders.sql):

INSERT INTO orders (order_id, customer_id, status, total_amount, item_count, currency, ship_country, notes, created_at, is_paid) VALUES ('f47ac10b-...', 'a1b2c3d4-...', 'shipped', 349.75, 3, 'USD', 'US', 'Please leave at front door.', '2024-02-10', true);

Multi-Table Config

Generate multiple related tables in a single run.

target:
  type: json
  to_path: /tmp/mockdata

tables:
  - name: categories
    row_count: 5
    columns:
      - id: serial()
      - name: random_in_string(Electronics|Clothing|Books|Home|Sports)
      - code: random_string(len=4,case=upper)

  - name: products
    row_count: 50
    columns:
      - id: uuid()
      - sku: random_string(len=8,case=upper)
      - name: random_string(min=5,max=30)
      - price: random_decimal(min=1,max=999)
      - stock: random_number(min=0,max=500)
      - is_available: random_boolean()
      - created_at: random_date()

  - name: customers
    row_count: 25
    columns:
      - id: uuid()
      - first_name: random_first_name()
      - last_name: random_last_name()
      - email: random_email()
      - phone: random_phone()
      - city: random_city()
      - country: random_country2()
      - joined_at: random_date()

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